(2,34 + x) − 8,5 = 4,73
2,34 + x = 4,73 + 8,5
2,34 + x = 13,23
x = 13,23 − 2,34
x = 10,89
Ответ: x = 10,89

Вычисления:
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}\mathrm{4,73}\\ \mathrm{8,50}\end{array}}\\ \begin{array}{r}\mathrm{13,23 }\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}\mathrm{13,23}\\ \mathrm{2,34}\end{array}}\\ \begin{array}{r}\mathrm{10,89 }\end{array}\end{array}$

(x − 20,8) + 12,17 = 22,2
x − 20,8 = 22,2 − 12,17
x − 20,8 = 10,03
x = 10,03 + 20,8
x = 30,83
Ответ: x = 30,83

Вычисления:
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}\mathrm{22,20}\\ \mathrm{12,17}\end{array}}\\ \begin{array}{r}\mathrm{10,03 }\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}\mathrm{10,03}\\ \mathrm{20,80}\end{array}}\\ \begin{array}{r}\mathrm{30,83 }\end{array}\end{array}$

(64,2 − a) − 1,28 = 3,242
64,2 − a = 3,242 + 1,28
64,2 − a = 4,522
a = 64,2 − 4,522
a = 59,678
Ответ: a = 59,678

Вычисления:
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}\mathrm{3,242}\\ \mathrm{1,280}\end{array}}\\ \begin{array}{r}\mathrm{4,522 }\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}\mathrm{64,200}\\ \mathrm{4,522}\end{array}}\\ \begin{array}{r}\mathrm{59,678 }\end{array}\end{array}$

5,05 − (y − 0,76) = 2,075
y − 0,76 = 5,05 − 2,075
y − 0,76 = 2,975
y = 2,975 + 0,76
y = 3,735
Ответ: y = 3,735

Вычисления:
$\begin{array}{r}\begin{array}{r}-\end{array}\underline{\begin{array}{r}\mathrm{5,050}\\ \mathrm{2,075}\end{array}}\\ \begin{array}{r}\mathrm{2,975 }\end{array}\end{array}$
 
$\begin{array}{r}\begin{array}{r}+\end{array}\underline{\begin{array}{r}\mathrm{2,975}\\ \mathrm{0,760}\end{array}}\\ \begin{array}{r}\mathrm{3,735 }\end{array}\end{array}$